Learning something new as a PHP programmer

Hello. For a few of years now I've been programming in PHP and recently I though it would be a good idea to start learning something new to add to my skill set (preferably something that can also be used in web development and is cross-platform) and one of the choices was Java.

I've done some programming in Java so I'm not quite clueless about it (but not far either). My question is, how much would it take to reach the same level of knowledge in Java that I have in PHP (or anyone with 3-5 years experience) and would it be worth it (here I'm referring to the ease of finding a job, at least paid the same if not better, etc)?

The target here is not necessarily to switch from PHP to Java (or any other language) but to be able to choose the best tool for the job.

Also if Java isn't really an option what would you recommend? (as a reference one of the things that I don't like about PHP is that is isn't strong typed)

If you're still considering web development then I would go the .NET route instead. PHP and .NET dominate web development, with Java coming up in third place.

I am still considering web development, but I don't want to replace PHP with Java, just use Java for parts of an application if required. Also if I were to completely switch from PHP to Java it wouldn't be for web development.

Regarding .NET, I don't really like it since I would only be able to develop applications for Windows.